MANILA, PHILIPPINES — The Philippines on Friday rejected a Chinese demand that it remove a grounded navy ship from a disputed shoal in the South China Sea, saying the vessel is a permanent government outpost.

China’s coast guard prevented two Philippine civilian vessels from delivering supplies to the rusting ship at Second Thomas Shoal on Sunday, escalating tensions in the area. The Philippines and the U.S. have called Beijing’s action provocative. The shoal is called Ayungin in the Philippines and Ren’ai Reef in China.

The ship “was placed in Ayungin Shoal in 1999 to serve as a permanent Philippine government installation in response to China’s illegal occupation of Mischief Reef in 1995,” Department of Foreign Affairs spokesman Raul Hernandez said in a statement Friday. Mischief Reef is another Philippine-claimed outcropping in the disputed Spratly islands in the South China Sea.

“The Philippines reiterates that Ayungin Shoal is part of its continental shelf over which the Philippines has sovereign rights and jurisdiction,” Hernandez said.

Philippine officials have previously said the military hospital ship ran aground in 1999 on the shallow coral reef and could not be removed because of a lack of funds and capability. Friday’s statement was the first acknowledgement that the ship was deliberately sent to the shoal as a government outpost.

China claims virtually the entire South China Sea, resource-rich waters where other neighboring nations also have claims.

On Thursday, a Philippine security official said the navy would send supplies on other vessels to the soldiers stationed on the grounded ship because the men were running short of food and water. The official, who did not want to be identified because he was not authorized to discuss the matter with the media, did not say when the supplies would be dispatched.

He said a small navy plane had dropped several days’ worth of drinking water to the troops.

“It’s not that we’re trying to court China’s ire,” he said. “We do not want to starve our people to death.”